Metallic glasses, also known as amorphous metals, have generated much interest for their potential as robust engineering materials. Metallic glasses are characterized by their disordered atomic-scale structure in spite of their metallic constituent elements—i.e. whereas conventional metallic materials typically possess a highly ordered atomic structure, metallic glasses are characterized by their disordered atomic structure. Notably, metallic glasses typically possess a number of useful material properties that can allow them to be implemented as highly effective engineering materials. For example, metallic glasses are generally much harder than conventional metals, and are generally tougher than ceramic materials. They are also relatively corrosion resistant, and, unlike conventional glass, they can have good electrical conductivity.
Nonetheless, the manufacture and implementation of metallic glasses present challenges that limit their viability as engineering materials. In particular, metallic glasses are typically formed by raising a metallic glass above its melting temperature, and rapidly cooling the melt to solidify it in a way such that its crystallization is avoided, thereby forming the metallic glass. The first metallic glasses required extraordinary cooling rates, e.g. on the order of 106 K/s, to avoid crystallization, and were thereby limited in the thickness with which they could be formed because thicker parts could not be cooled as quickly. Indeed, because of this limitation in thickness, metallic glasses were initially largely limited to applications that involved coatings. Since then, however, metallic glass compositions that have lower critical cooling rates have been developed, which can thereby form metallic glasses at much lower cooling rates, and can therefore be made to be much thicker (e.g. greater than 1 mm), for example via die casting. These thicker metallic glasses are known as ‘bulk metallic glasses’ (“BMGs”).